Re: [PATCH v2 3/9] tty: serial: fsl_lpuart: handle EPROBE_DEFER for DMA
From: Rob Herring <robh+dt@kernel.org>
Date: 2020-02-27 22:34:48
Also in:
linux-devicetree, linux-serial, lkml
On Fri, Feb 21, 2020 at 11:48 AM Michael Walle [off-list ref] wrote:
The DMA channel might not be available at the first probe time. This is esp. the case if the DMA controller has an IOMMU mapping. Use the new dma_request_chan() API and handle EPROBE_DEFER errors. Also reorder the code a bit, so that we don't prepare the whole UART just to determine that the DMA channel is not ready yet and we have to undo all the stuff. Try to map the DMA channels earlier.
Changing this means you never probe successfully if you boot a kernel with the DMA driver disabled (or it's IOMMU disabled). Some other drivers request DMA in open() and can work either way. Rob _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel